157 



VOL. LXXXVII.] PHILOSOPHICAL TRANSACTIONS. 



Thinking it might perhaps be more satisfactory to know the real strength of the 

 identical iron of which the barrel used in the before-mentioned experiment was 

 constructed, rather than to rest the determination of the strength of the barrel on 

 the decision of the strength of iron taken from another parcel, and which 

 very possibly might be of a different quality, since writing the above, I have taken 

 the trouble to ascertain the strength of the iron of which the barrel was made, 

 which was done in the following manner. Having the one half of the barrel 

 still in my possession, I caused small pieces, 2 inches long, and about -£- of an inch 

 square, to be cut out of the solid block, in the direction of its length, with a fine 

 saw ; and these pieces being first made round in their middle by filing, and then 

 by turning in a lathe with a very sharp instrument, were reduced to such a size as 

 was necessary, in order to their being pulled asunder in my machine for measuring 

 the strength of bodies. In this machine the body to be pulled asunder is held fast 

 by 2 strong vices, the one fastened to the floor, and the other suspended to the 

 short arm of a Roman balance, or common steel-yard ; and in order that the bo- 

 dies so suspended may not be injured by the jaws of the vices, so as to be weakened 

 and to vitiate the experiments, they are not made cylindrical, but larger at their 

 two ends where they are held by the vices, and from thence their diameters were 

 gradually diminished towards the middle of their lengths, where their measures 

 are taken, and where they never fail to break. As I had found by the results 

 of many experiments which I had before made on the strength of the various me- 

 tals, that iron, as well as all other metals, is rendered much stronger by hammer- 

 ing, I caused those pieces of the barrel which were prepared for these experiments 

 to be separated from the solid block of metal, and reduced to their proper sizes, by 

 sawing, filing, and turning, and without ever receiving a single blow of a hammer ; 

 so that there is every reason to believe that the strength of the iron, as determined 

 by the experiments, may safely be depended on. The results of the experiments 

 were as follow : 



Experi- 

 ments. 



Diameter of the 

 Cylinder at the 

 Fracture. 



Area of a transverse 

 section of the Cy- 

 linder at the Frac- 

 ture. 



Inch. 







6 6 







7 6 



Inch. 



T"0"9"-"2"9" 



1 



3 5 3 ."B" 8 



1 



ITT. T 



i 

 ■3"~ao. T 



Weight required to break it. 

 lbs. avoirdupois. 



123.18 

 182. 

 22075 

 277-01 



Weight required to break l 

 inch of this iron, 

 lbs. avoirdupois. 



62737 



64366 

 64526 

 61063 



Number of experiments = 4) 452692 



Mean 63173 



merits. Thus then it appears, that the deduction of the enormous exaggeration of the initial force of the 

 elastic fluid is entirely owing to the improper and unnatural mode of deducing it from a comparison with 

 each other, of things of an incongruous and incommensurable nature. In such ways the most monstrous 

 conclusions may be deduced preposterously from premises the most simple and certain in their own 

 nature. 



